Size segregated aerosol mass concentration measurement with inlet conditioners and multiple detectors

ABSTRACT

A system for measuring size segregated mass concentration of an aerosol. The system includes an electromagnetic radiation source with beam-shaping optics for generation of a beam of electromagnetic radiation, an inlet sample conditioner with adjustable cut-size that selects particles of a specific size range, and an inlet nozzle for passage of an aerosol flow stream. The aerosol flow stream contains particles intersecting the beam of electromagnetic radiation to define an interrogation volume, and scatters the electromagnetic radiation from the interrogation volume. The system also includes a detector for detection of the scattered electromagnetic radiation an integrated signal conditioner coupled to the detector and generating a photometric output, and a processor coupled with the conditioner for conversion of the photometric output and cut-size to a size segregated mass distribution.

RELATED APPLICATIONS

The present application is a continuation-in-part and claims priority toU.S. patent application Ser. No. 12/187,827, filed Aug. 7, 2008, whichclaims the benefit of U.S. Provisional Application No. 60/964,008, filedAug. 8, 2007, both of which are incorporated by reference herein intheir entirety. This application further claims the benefit of thefiling dates of U.S. Provisional Application No. 61/152,084, filed Feb.12, 2009, and of U.S. Provisional Application No. 61/303,547, filed Feb.12, 2010, both of which are incorporated by reference herein in theirentirety.

FIELD OF THE INVENTION

The present disclosure relates generally to the detection of particles,and more specifically to the measurement of dust particle concentrationsand size distributions.

BACKGROUND OF THE INVENTION

Human exposure to aerosols from indoor, outdoor, or workplace causesadverse health effects. The United States Environmental ProtectionAgency (EPA) promulgates regulations on PM10 (mass of particles withaerodynamic diameters less than approximately 10 μm) and PM2.5 (mass ofparticles with aerodynamic diameters less than approximately 2.5 μm).The American Conference of Governmental Industrial Hygienists (ACGIH)has also established regulations on respirable, thoracic and inhalableaerosols, defined as particles having aerodynamic diameters of less than4 μm, 10 μm, and 100 μm respectively. A discussion of the variousregulations are found at National Primary and Secondary Ambient AirQuality Standards, 40 Code of US Federal Regulation, Chapter 1, Part 50(1997) and Vincent, J. H., Particle Size-Selective Sampling forParticulate Air Contaminants Cincinnati, ACGIH (1999), both of which arehereby incorporated by reference except for explicit definitionscontained therein.

Presently, the federal reference method (FRM), which utilizes filtersamplers, is implemented to determine compliance with mass based airquality standards. The particle size collected by the filter samplers isdetermined by a size selective inlet. Typically, the filter methodrequires a relatively long sampling time, about 24 hours, to collectenough mass on the filter, with the results not being available untilthe samples are analyzed in the laboratory.

Direct-reading instruments provide near real-time measurement of aerosolmass concentrations. For example, a photometer can be calibrated tosurrogate fine particle mass concentration over a wide concentrationrange. But it does not provide size information. On the other hand, anoptical particle counter (OPC) or aerodynamic particle sizer (APS) mayprovide very high resolution size distributions. But these instrumentsonly work at relatively low concentrations due to coincidence errors.

U.S. Patent Publication Number US 20090039249A1 (U.S. patent applicationSer. No. 12/187,287) commonly assigned to the assignee of the presentinvention, and to which the present application claims priority,discloses an invention that combines photometry and optical oraerodynamic particle sizing in one optical device for measuring sizesegregated mass concentrations, for example, PM10, PM2.5 and PM1, orinhalable, thoracic and respirable fractions, in real time. The opticaldevice features a single optical chamber and a single detector. Such adesign reduces instrument components and simplifies the instrumentconfigurations. However, such a design may pose challenges to measuringvery low concentrations using photometric signals.

Optical or aerodynamic sizing requires highly focused light beam(s) toproduce a strong scattering pulse. To achieve a highly focused lightbeam, optics having shorter focal lengths are typically employed. Suchoptics have wide convergence/divergence angles, thus bathing largersurface areas. For example, optics and light traps can create a largeamount of stray light, and cause great difficulties to designapparatuses, for example apertures, in reducing stray light. Because thephotometric signal is detected by the same detector in the same opticschamber, the stray light causes low signal-to-noise levels of thephotometric measurement at very low concentrations, for example, atconcentrations in the range of 0.1-1 μg/m³. The stray light also causesbackground photometric signal drift at different environmenttemperatures.

SUMMARY OF THE INVENTION

Embodiments of the claimed invention achieve real-time size segregatedmass concentration measurement over a wide concentration range. Thedifficulties related to the combined photometry and optical/aerodynamicsizing due to a single detector and/or a single optical chamber aresignificantly reduced in some embodiments, while at the same time,measurement accuracy is improved.

Various embodiments of the invention include a hybrid apparatus and/ormethod for determining the particle size distribution and massdistributions in the particle size range of interest (collectivelyreferred to herein as size segregated aerosol mass concentration) and inreal time. The disclosed device may have multiple detectors, radiationsources with multiple wavelengths or multiple optics chambers. Acut-size adjustable sample conditioner may be applied to the inlet ofthe device. This device may provide a simultaneous and real timeindication of the size segregated mass concentration of the interrogatedparticle stream. The measurement may be performed on particles suspendedin a medium such as a liquid, a gas or some combination thereof When themedium is a gas, the product is known as an aerosol. The gas may be air,nitrogen, argon, helium, carbon dioxide or any other gas or gasmixtures. Particles can be solid, liquid or a combination of both.

Structurally, certain embodiments of the invention implement incidentbeams of electromagnetic radiation (hereinafter “light beam”) thatdefine interrogation volumes through which a suspended particle streampasses. A portion of the light that is scattered from the interrogationvolumes by the particles may be sensed by detectors. In someembodiments, the detectors generate an electrical signal proportional tothe scattered light received from particles. The electrical signal maybe processed by one or multiple signal conditioning circuits, including:(1) an integrated photometric signal proportional to the intensity ofincident light that is scattered by the particle or ensemble ofparticles in the interrogation volume and intercepted by the detector;(2) a pulse height signal derived from scattered light originating fromindividual particles; and (3) a time-of-flight signal providing a director indirect measurement of the particle velocity through theinterrogation volume region. The integrated signal may comprise a biasedor time-averaged signal that can be correlated to particle massconcentration, especially if the particles within the interrogationvolume are made of primarily fine or respirable particles. The pulseheight signal may be indicative of the particle optical equivalent size.The time-of-flight signal may be indicative of the particle aerodynamicdiameter. Given the properties of the particles (e.g. shape, refractiveindex, density), the mass concentration may be inferred from theparticle size distribution. The mass concentration can be obtained byperforming mathematical operations on the detected signals, from whichthe size segregated mass fractions such as PM1, PM2.5, PM10, inhalable,thoracic and respirable may be obtained.

Some embodiments of the invention measure size segregated massconcentrations using a single optical chamber and a single detector witha cut-size adjustable inlet conditioner. The inlet conditioner may becontrolled to allow only particles of a certain size range to enter theintegration volume at a time. The optical system may be optimized fordetecting the total light scattering from all particles in theintegration volume. The integrated photometric signal generated fromtotal light scattering may be correlated to aerosol mass concentration.The size segregated mass concentration may be inferred by scanning thetwo or more mass fractions through the inlet conditioner.

Some embodiments of the invention measure size segregated massconcentrations using a single optical chamber and multiple detectors.Each detector may be optimized for one kind of optical signal. Forexample, one detector may be optimized for the integrated photometricsignal, and one for the pulse height or time-of-flight signal.

Some embodiments of the invention measure size segregated massconcentrations with multiple optics chambers, each optimized for onekind of signal. For example, one chamber optimized for measuring theintegrated photometric signal, and the other optimized for the pulseheight or time-of-flight signal. These chambers could be in oneinstrument or in multiple instruments that are connected electrically.

Some embodiments of the invention measure size segregated massconcentrations with multiple optics chambers that only measure theintegrated photometric signal. Each chamber is equipped with an inletsample conditioner that selects particles of a certain size range toenter the integration volume.

Some embodiments of the invention improve the measurement accuracy andextend the particle size range with multiple radiation sources withdifferent wavelengths. Since the light scattering sensitivity depends onthe wavelength of the illuminating radiation. A shorter wavelength maybe optimized for measuring smaller particles, while a longer wavelengthmay be optimized for larger particles.

A representative and non-limiting sensitive size range for the variousembodiments of the invention is from 0.1 μm to 20 μm. A non-limitingdynamic range of particle mass concentration is 0.0001 to 400 mg/m³.Certain embodiments may include an optional filter installed downstreamof the optical chamber to collect particles for direct mass measurement.Other appurtenances include devices for controlling parameters such aslight power and flow.

Some embodiments of this invention describe devices and methods thatimprove the instrument operation reliability, measurement accuracy andease of use. Examples include an integrated touch screen for a userinterface, an internal algorithm to determine a conversion from lightscattering pulse height to aerodynamic particle diameter, and anEthernet connection for instrument communication.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a size segregated mass concentrationmeasuring device having a single optical chamber, single integratedphotometric detector, and using a cut-size adjustable inlet sampleconditioner to control the particle size entering the optical chamber,according to an embodiment of the invention;

FIG. 2 is a schematic diagram of a size segregated mass concentrationmeasurement device having a single optical chamber and multiple,specific-signal optimized detectors, according to an embodiment of theinvention;

FIG. 3 is a schematic diagram of a size segregated mass concentrationmeasurement device having multiple optical chambers, each optimized fora specific kind of signal, according to an embodiment of the invention;

FIG. 4 is a schematic diagram of a size segregated mass concentrationmeasurement device having multiple inlet conditioners and multipleoptical chambers, according to an embodiment of the invention; and

FIG. 5 is a schematic diagram of a size segregated mass concentrationmeasurement utilizing radiation sources of multiple wavelengths,according to an embodiment of the invention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, a schematic diagram of adjustable cut-sizesegregated mass concentration measurement system 300 is depicted in anembodiment of the invention. System 300 includes adjustable cut-sizeaerosol measurement section 302 coupled to a control system, such assignal acquisition and processing system (SAPS) 304.

Aerosol measurement section 302 includes an adjustable inlet portion306, detection portion 308, optional filter 310, and pumping system 312.Adjustable inlet portion 306 and pumping system 312 are operably coupledto detection portion 308, with pumping system 312 coupled through outletfilter 310.

In the embodiment depicted in FIG. 1, adjustable inlet portion 306includes inlet 314 coupled to adjustable cut-size inlet sampleconditioner 316. Adjustable inlet portion 306 may include a sheath flowconditioning loop 318 having a filtration device 320 and flowcontrolling and measuring device 322. In one embodiment, flowcontrolling and measuring device 322 may comprise an orifice.

Adjustable cut-size inlet sample conditioner 316 may include, but not belimited to the following forms: (1) an impactor with adjustablecut-size, through, for example, scanning flowrate or changing nozzlesize; (2) a cyclone with adjustable cut-size, through, for example,scanning flowrate or changing physical dimensions; (3) a rotatingdevice, for example, a fan, with adjustable speed. Adjustable cut-sizeinlet sample conditioner 316 may also include an inlet cut-sizecontroller 364 as discussed below in further detail.

Detection portion 308 includes optics chamber 324, light source 326emitting light beam 328, light trap 330, light collecting optics 332,light detector 334 with light detector output signal 336, and outletnozzle 337. Optics chamber 324 defines viewing or interrogation volume338. Light beam 328 may include scattered portion 342 and unscatteredportion 344. Scattered portion 342 includes collected scattered light343 incident on light detector 334. Light detector 334 may comprise anynumber of known detectors, including a photodiode or a photomultipliertube.

Detector portion 308 and light detector 334 may be adapted or optimized(e.g. detector type, sensitivity range, location, etc.) to detect aparticular particle or light characteristic, including overall intensityof scattered light 343, pulse-height, time-of-flight (pulse width) orother such characteristics. In other embodiments, detector portion 308may be adapted to detect light emitted from the particles as a result ofthe intersection of light beam 328 and the particles. In the embodimentdepicted, detector portion 308 and light detector 334 are adapted todetect and determine scattered light intensity.

Light source 326 and emitting light beam 328, may be electromagneticradiation sources such as a diode laser, an LED or a lamp (broadband orline emitting), or other similar light source.

Detection portion 308 may also include optional beam-shaping optics 346that may include a lens such as a cylindrical lens. The shaping opticsmay additionally or alternatively comprise reflective components such asmirrors, or fiber optic components (not depicted). Filter 310 in oneembodiment may comprise a gravimetric filter 310 coupled to outletnozzle 337 of detection portion 308. Filter 310 is in turn operablycoupled to pump system 312. In other embodiments, filter 310 may not bepresent in system 300, such that pumping system 312 is coupled directlyto outlet nozzle 337.

As depicted in the embodiment of FIG. 1, pumping system 312 includesprotection filter 350, flowmeter 352, flow pulsation damping chamber 354and pump or blower 356 that may be ducted to an exhaust. Numerous kindsof pumps or blowers 356 may be utilized, including, but not limited to,a diaphragm pump, a rotary vane pump, a piston pump, a roots pump, alinear pump or a regenerative blower.

Still referring to FIG. 1, control system SAPS 304 in one embodimentincludes signal conditioner 360, processor 362, adjustable inlet sampleconditioner controller 364, and output device 366.

Signal conditioner 360 may include hardware, such as a signalconditioning circuit, and software to condition light detector outputsignal 336, and deliver one or more conditioned signals 368. Processor362 may comprise a digital microprocessor, microcontroller, or similarprocessing device, and may also include memory for storing data,algorithms, instructions, or other information.

Output device 366 may comprise data representing size segregated massconcentration and optionally may include devices for displaying and/orstoring such data, such as display, a storage device, analog output or acomputer.

In operation, an incoming flow stream 370 comprising particles 372 maybe drawn through inlet 314 and passed through inlet sample conditioner316. Inlet sample conditioner 316 may only allow particles 372 of agiven size range to get through, and the penetration size range may beadjusted during the course of measurement, either manually, bycontroller 364, or a combination thereof.

Flow stream 370 may then be split into a sheath flow stream 374 and anaerosol flow stream 376. Sheath flow stream 374 may be diverted tosheath flow conditioning loop 318 and through filtration device 320 andflow measuring device 322.

Aerosol flow stream 376 passes through an inlet nozzle 307 to opticschamber 324 and viewing or interrogation volume 338. Interrogationvolume 338 may be defined by the intersection of light beam 328 andaerosol flow stream 376.

As discussed above, size segregated mass concentration measurementsystem 300 may further comprise beam-shaping optics 346 that may includea lens such as a cylindrical lens. Beam-shaping optics 346 shape orfocus light beam 328 prior to, or at, entry into optics chamber 324.

Within optics chamber 324, light beam 328 is scattered by particles 372forming scattered portion 342 and unscattered portion 344. Scatteredportion 342 dispersed at a solid angle A may be subtended by lightcollection system 332 or radiation collector (e.g. a spherical mirror,aspheric condenser lenses, or other electromagnetic radiation collectiondevices available to the artisan) within optics chamber 324. The angle Afrom which scattered light 342 is collected may be in the range of 0degrees to 360 degrees. Unscattered portion 344 of light beam 328 may becaptured by light trap 330.

Inner surfaces of optics chamber 324 may be coated with a black or highabsorptivity coating such as an anodized coating. Collected light 343gathered by light collecting system 332 may be transferred to detector334. Light detector 334 may produce an electrical signal 336proportional to the convolution of the incident electromagneticradiation and the spectral sensitivity of detector 334.

In some embodiments, aerosol flow stream 376 exits optics chamber 324through outlet nozzle 337 and may be passed through filter 310, whichmay be weighed to obtain mass concentration or be analyzed for chemicalcomposition. Aerosol flow stream 376 may be drawn through optics chamber324 by pumping system 312.

Signal conditioner 360, which in one embodiment is an integratedphotometric signal conditioning circuit, generates integrated outputs368 proportional to intensity, or watt density of the collected lightgathered by the radiation collector and incident on the detector 334.The outputs are in turn proportional to the light flux scattered fromall the particles classified by the inlet sample conditioner in theinterrogation volume region. The outputs may be routed to processor 362for analysis. This information is combined with the inlet conditioner316 known particle cut-size to calculate size segregated massconcentration distributions. The result can be output to output device366, for display, storage, transfer, or other use.

Referring to FIG. 2, size segregated mass concentration measurementsystem 400 differs from system 300 with respect to both aerosol inletand particle detection. System 400 includes aerosol measurement section402 coupled to a control system, such as SAPS 404.

Aerosol measurement section 402 includes an inlet portion 406 anddetection portion 408. Although not depicted, it will be understood thatinlet portion 406 may also include sheath flow, and aerosol measurementsection 402 may also include optional filter 310, and pumping system 312as previously depicted and described with reference to system 300 andFIG. 1. Inlet portion 406 and pumping system 312 are operably coupled todetection portion 408, with pumping system 312 optionally coupledthrough outlet filter 310.

In the embodiment depicted in FIG. 2, detection portion 408 includesoptics chamber 424, light source 456 emitting light beam 428, light trap430, light collecting optics 432, light detectors 434 a and 434 b withrespective light detector output signals 436 a and 436 b, and outletnozzle 437. Although only two detectors are depicted, it will beunderstood that more than two detectors may be used.

It is also understood that the collection optics 432 may have multiplecomponents, such as depicted 432 a and 432 b, each positioned to collectscattered light at optimal angles. In other embodiments, collectingoptics 432 is substantially similar to collecting optics 332 of system300.

Light detection portion 408, including light detectors 434 a and 434 bmay be especially adapted to respectively detect one or more particularcharacteristics of the particles or scattered portion 442 of light beam428. Such characteristics include intensity of scattered light 343,light pulse-height, time-of-flight (pulse width) or other suchcharacteristics. It will be understood that a “pulse” generally refersto a pulse of scattered light as measured by light detector 434, andhaving a peak measured value, or pulse height, typically measured involts, over a period of time, the pulse width.

Detector portion 408 and light detectors 434 may be adapted or optimizedin a number of different ways. For example, a detector 434 may bedesigned to specifically detect and measure pulses, including eitherpulse height, width, measure particular wavelengths, or to have aparticular sensitivity range. In other embodiments, a detector 434 maybe located or positioned in a particular way to detect and measure aparticular characteristic. In other embodiments, detector portion 408and a detector 434 may be adapted to detect light fluoresced from theparticles as a result of the intersection of light beam 328 and theparticles.

In other embodiments, detector 434 a may be combined with one componentof the collecting optics 432 to collect more forward-scattering light,which yields a more sensitive integrated photometric signal. On theother hand, the detector 434 b may be combined as one component of thecollecting optics 432 to collect scattered light in a wide-angle range,so that the pulse height signal is a more monotonic and smooth functionof particle size. Furthermore, a slower detector 434 a may be used toaverage the integrated photometric signal, while a faster detector 434 bmay be used for pulse height or time-of-flight measurement.

In the embodiment depicted, light detector 434 a is adapted to detectscattered light in a manner most conducive to determining lightintensity. Light detector 434 b is adapted to measure either pulseheight or time of flight (pulse width). In another embodiment, a thirdlight detector may be used, the third detector 434 measuring a thirdcharacteristic. Any individual characteristic, or a combination of thesecharacteristics, may be used by the control system, SAPS 404, todetermine mass concentration by size.

Optics chamber 424 defines viewing or interrogation volume 438. Lightbeam 428 may include scattered portion 442 and unscattered portion 444.Scattered portion 442 includes collected scattered light 443 incident onlight detectors 434 a and 434 b. Light detectors 434 a and 434 b maycomprise any number of known detectors, including a photodiode or aphotomultiplier tube.

Light source 456 emitting light beam 428 may be an electromagneticradiation source such as a diode laser, an LED or a lamp (broadband orline-emitting), or other similar light source.

Detection portion 408 may also include optional beam-shaping optics 446that may include a lens such as a cylindrical lens. The shaping opticsmay additionally or alternatively comprise reflective components such asmirrors, or fiber optic components (not depicted).

As depicted in FIG. 2, the control system comprises SAPS 404, whichincludes two or more conditioners 460. Each of the conditioners 460 maybe adapted to condition a signal from a detector 434 associated with aparticular characteristic. In the depicted embodiment, signalconditioner 460 a is adapted to condition a signal from detector 434 afor determining intensity. Conditioner 460 a is communicatively coupledto detector 434 a and receives signal 436 a. Signal conditioner 460 b iseither adapted to condition a pulse height or time-of-flight signal 436b from detector 434 b. In other embodiments, SAPS 404 includes three ormore conditioners 460. For example, SAPS 404 may include an integratedsignal conditioner, pulse height conditioner, coupled to time of flightconditioner, and their respective detectors 434.

SAPS 404 also includes processor 462, and though not depicted in FIG. 2,it will be understood that SAPS 404 may also generally include an outputdevice 366 communicatively coupled to processor 462.

Similar to system 300 described above, in operation an incoming flowstream 470 comprising particles 472 may be drawn through inlet 414.However, in this embodiment, incoming flow stream 470 is not conditionedby passing through an adjustable inlet sample conditioner.

Flow stream 470 passes through inlet nozzle 437 to optics chamber 424and viewing or interrogation volume 438. Beam-shaping optics 446 mayshape or focus light beam 428 prior to, or at, entry into optics chamber424.

Within optics chamber 424, light beam 428 is scattered by particles 472forming scattered portion 442 and unscattered portion 444. Scatteredportion 442 is dispersed at a solid angle A and may be subtended bylight collection system 432 or radiation collectors within opticschamber 424. The angle A from which scattered light is collected may bein the range of 0 degrees to 360 degrees. Unscattered portion 444 oflight beam 428 may be captured by light trap 430.

In this embodiment, pulse height or time-of-flight conditioner 460 bprovides a signal representative of optical or aerodynamic particle sizedistribution, which is combined with the integrated photometric signal460 a at processor 462 to produce size segregated mass distribution.

As an alternative to, or in addition to, either the pulse heightmeasurement or the time-of-flight measurement, the pulse height andpulse width can be multiplied or integrated in a convolution integral byprocessor 462 to produce an “area” measurement of the signal pulse. Thearea product can be used to infer particle size. Herein, “area” isgenerally considered to be some product of the pulse width and the pulseheight. In one embodiment, “area” is the pulse height multiplied by thepulse width. In another embodiment, “area” is determined by digitizingthe pulse with sufficient resolution to perform a numerical integrationof the pulse signal over the duration of the pulse. The errorsassociated with particle sizing when using pulse measurement techniquescan be reduced by using pulse area to size particles instead of usingpulse height or amplitude. See U.S. Provisional Patent Application No.61/303,547 to Farnsworth et al., assigned to the assignee of the presentapplication, the disclosure of which is included in Appendix A and whichis incorporated by reference herein in its entirety except for expressdefinitions therein.

For a particle of a given size, the pulse height or amplitude producedby the particle will typically be at a maximum when the trajectory isthrough the center of the measurement volume. Conversely, the pulsewidth produced by such a particle will typically be maximized near theedges of the measurement volume. The pulse area profile produced by agiven particle is less dependent on the trajectory through theinterrogation volume than either the pulse height or the time-of-flightcomponents that make up the pulse area indication. Accordingly, aproduct (i.e. area) of the two profiles yields a profile more uniform(less sensitive to the position within the measurement volume) thaneither of its components. Sizing based on pulse area allows the designerto counterbalance these two profiles, resulting in a more uniform sizemeasurement throughout the measurement volume.

Size measurement by pulse height can place a limit on the size of theparticle that can be measured. The limit is determined by the outputlimit of the detector circuit. If a particle scatters enough light torail the detector circuit, the peak of the pulse signal will be“clipped.” Pulse width, on the other hand, will continue to increaseregardless of whether the detector signal is clipped, thus extending thesize range of a pulse area measurement. Therefore, the effects of thelimit on pulse height measurements are mitigated by using pulse area tosize particle.

It is noted that area-based signal processing is known to improve OPCsize resolution, but the prevailing belief is that the velocity profileacross the nozzle must be uniform for the area measurement to have anyvalue. See Aerosol Measurement, 2^(nd) ed. (2001) edited by Baron andWilleke, pg 438, the disclosure of which are hereby incorporated byreference except for definitions expressly defined therein. Accordingly,existing devices utilize sheath flows to accomplish uniform velocityprofiles.

Because of the inverse relationship between the particle velocity andbeam intensity profiles, the pulse area technique disclosed hereinprovides sufficient accuracy and resolution without the use of sheathflows, and can extend the dynamic range of pulse measurement techniquesgenerally.

Therefore, by using detectors 434 and conditioners 460 adapted to detectand condition specific characteristics, system 400 improves themeasurement accuracy, and extends the measurement size and concentrationrange, as compared to single detector-conditioner systems.

Referring to FIG. 3, system 500 having multiple optical chambers isdepicted in an embodiment of the invention. System 500 includes twoaerosol measurement sections 502 a and 502 b, coupled to a controlsystem, which in one embodiment is a single SAPS 504. It will beunderstood that in other embodiments, system 500 may include more thantwo sections 502.

Each aerosol measurement section 502 includes an inlet portion 506 anddetection portion 508. Although not depicted, it will be understood thateach inlet portion 506 may have sheath flow 318, each aerosolmeasurement section 502 may also include optional filter 310, andpumping system 312 as previously depicted and described with referenceto system 300 and FIG. 1. Inlet portions 506 and pumping systems 312 areoperably coupled to detection portions 508, with pumping systems 312optionally coupled through outlet filters 310. In other embodiments, asingle filter 310 and pumping system 312 may serve multiple aerosolmeasurement sections 502.

Each detection portion 508 includes an optics chamber 524, light source526 emitting light beam 528, light trap 530, light collecting optics532, light detectors 534 with light detector output signal 536, andoutlet nozzle 437.

Detection portions 508 a and 508 b, and their respective detectors 534 aand 534 b, may be especially adapted to detect a particularcharacteristic of scattered portion 442 of light beam 428. Similar tothe detection portions 408 and detectors 434 described above, detectionportions 508 a and 508 b may be adapted or optimized to detect aparticular characteristic such as light intensity, pulse height,time-of-flight (pulse width) or another such characteristic.

In the depicted embodiment, detection portion 508 a includes a singlechamber 524 a with detector 534 a and integrated signal conditioner 560a especially adapted and optimized to condition and output a signal 568a for determining a first characteristic, in this case, intensity, ofscatter portion 442 of light. Detection portion 508 b includes a singlechamber 524 b with detector 534 b adapted to detect a secondcharacteristic, in this case either pulse height and/or time-of-flight,and conditioner 560 b, which is adapted to condition signal 536 a andoutput representative of the second characteristic, in this case, pulseheight or time-of-flight signal 568 b.

As in other embodiments, light sources 526 emitting light beams 528 maybe electromagnetic radiation sources such as diode lasers, LEDs, lamps(broadband or line emitting), or other similar light sources. Detectionportion 508 may also include optional beam-shaping optics 546 that mayinclude lenses. The shaping optics may additionally or alternativelycomprise reflective components such as mirrors, or fiber opticcomponents (not depicted).

Conditioners 560 a and 560 b are each communicatively coupled to asingle processor 562, though in other embodiments, multiple processorsmay be used. System 500 operates similarly to the previously describedembodiments, though one optical chamber may be optimized to measure afirst characteristic, such as the integrated signal, and the other(s)may be optimized to measure a second characteristic, such as pulseheight or time-of-flight. Such a design eliminates the difficulties oftrying to measure two characteristics such as integrated signal andpulse height or time-of-flight in one optical chamber with a commondetector, where reducing background light scattering is very difficultdue to the short focal length needed to generate high intensity lightbeams for particle pulse measurement. Using multiple optical chambersintroduces flexibilities in optimizing each chamber for one type ofsignal, thus greatly improving measurement accuracy, and extending sizeand concentration range. Each measurement chamber may or may not shareperipheral components, such as inlet, filters, flowmeter and pump.

Referring to FIG. 4, system 600 with multiple optical chambers, eachequipped with an inlet sample conditioner, is depicted in an embodimentof the invention. System 600 includes two or more aerosol measurementsections 602 and a control system, SAPS 604. SAPS 604 includes two ormore signal conditioners 660 corresponding to the two or more aerosolmeasurement sections 602 communicatively coupled to digital processor662.

Each inlet portion 606 includes an inlet sample conditioner 616. Inletsample conditioner 616 a is adapted to restrict the range of allowedparticle size to a predefined particle size or range, while inlet sampleconditioner 616 b is adapted to restrict particle sizes to a second,different, predefined particle size or range. Inlet conditioners 616 maybe, but are not limited to, impactors, cyclones, virtual impactors orvirtual cyclones.

It will be understood that each detection portion 608 includessubstantially the same components as previously described detectionportions 508, operating in a similar manner. However, unlike system 500,because inlet portions 616 are adapted to restrict particle size, eachdetection portion 608 may only detect or measure the integratedphotometric signal of the particle size selected by its respective inletsample conditioner 616. Results from each aerosol measurement system 602may be combined to produce size segregated mass distribution viaconditioners 660 and processor 662.

The advantages of the design of system 600 are that (1) background lightreduction difficulties are avoided when a single chamber was used forboth integrated signal and single particle sizing; (2) improvedflexibility in optics design; (3) since each chamber detects aphotometric signal, they may use very similar or common hardware andfirmware for signal processing, as well as a common algorithm forcalculating mass distributions.

Referring to FIG. 5, a dual wavelength system 700 is depicted in anembodiment of the invention. The dual wavelength system 700 includes asingle optical chamber and two light emission sources that propagatelight beams with different wavelengths. System 700 includes aerosolmeasurement section 702 coupled to a control system, which in thedepicted embodiment is SAPS 704.

Aerosol measurement section 702 includes an inlet portion 706 anddetection portion 708. Although not depicted, it will be understood thatinlet portion 706 may have a sheath flow conditioning loop 318, andaerosol measurement section 702 may also include optional filter 310,and pumping system 112 as previously depicted and described withreference to system 300 and FIG. 1. Inlet portion 706 and pumping system312 are operably coupled to detection portion 708, with pumping system112 optionally coupled through outlet filter 310.

Detection portion 708 includes optics chamber 724, light sources 726 aand 726 b emitting light beams 728 a and 728 b, respectively, optionallight traps 730 (not depicted), light collecting optics 732, lightdetectors 734 a and 734 b with respective light detector output signals736 a and 736 b, and outlet nozzle 737. Light detectors 734 a and 734 bmay be fitted with band pass filters 735 a and 735 b, respectively, andeach light detector 734 a and 734 b may be especially adapted to detecta particular characteristic of scattered portion 742 of the respectivelight beams 728 a and 728 b. Light sources 756 emitting light beams 728may be electromagnetic radiation sources such as diode lasers, LEDs,lamps (broadband or line emitting), or other similar light sources.

Optics chamber 724 defines viewing or interrogation volume 738.Detection portion 708 may also include optional beam-shaping optics 746that may include a lens such as a cylindrical lens, similar to thosedescribed above.

SAPS 704 include multiple conditioners 760, receiving multiple lightdetector output signals 736. In the embodiment depicted, conditioners760 include integrated signal conditioner 760 a communicatively coupledto detector 734 a and receiving signals 736 a, and optimal pulse heightor time of flight conditioner 760 b communicatively coupled to detectors734 a and receiving signals 736 a. Fluorescence conditioner 760 c iscommunicatively coupled to detector 734 b and receiving signals 736 b.

SAPS 704 can also include processor 762, and though not depicted in FIG.5, it will be understood that SAP 704 also generally includes an outputdevice 766, similar to those described above, communicatively coupled toprocessor 762.

In one embodiment, the light sources 726 a and 726 b may be selected toinclude wavelengths of emission that capitalize on certaincharacteristics of the aerosol. For example, light source 726 a may beselected to emit a wavelength that enhances the range of particles thatcan be detected in a scattering arrangement, such as discussedpreviously. Light source 726 b, meanwhile, may be selected to include awavelength or band pass known to fluoresce certain particles that are inthe aerosol. See, e.g., U.S. Pat. No. 6,831,279 to Ho, which is herebyincorporated by reference in its entirety except for express definitionstherein.

In operation, such an embodiment may utilize band pass filter 735 a todetect the scattering wavelength emitted by light source 726 a whileblocking out the other wavelengths present in optics chamber 724 (e.g.,wavelengths of light source 726 b and attendant fluorescencewavelengths). Likewise, filter 735 b can be utilized and selected todetect the fluorescence wavelength of the certain particles in theaerosol known to fluoresce while blocking out non-fluorescencewavelengths present in chamber 724 (e.g., wavelengths of lights sources726 a and 726 b).

In another embodiment, the wavelengths of both lights sources 726 a and726 b may be selected for scattering. The aerosol scattering response isa function of light wavelength. Typically shorter wavelengths producemore sensitive measurement for smaller particles, and longer wavelengthsproduce better measurement for larger particles. Using multiplewavelengths may improve the measurement accuracy, and extend theparticle size range. Scattering signals from multiple wavelengths mayyield extra information about particle properties, such as shape andrefractive index. Further, particles originating from living organismsand biogenetic species may generate fluorescence patterns whenilluminated by light with short wavelengths. Therefore, in addition toincreasing measurement accuracy, by examining the fluorescence patternsof particles, bio-origin particles may be identified.

With respect to systems 300 to 700 described above, those embodimentsinvolving measuring pulse height for particle sizing may have aninternal algorithm stored in their respective control systems todetermine a conversion from pulse height or optical size to aerodynamicsize, employing one or multiple aerodynamic classifiers (eg. impactorsor cyclones). This innovation guides a user through taking pulse heightdistribution with and without the aerodynamic classifiers. Finding thepulse height corresponding to 50% penetration of the aerosol beingtested, and comparing that to known aerodynamic cut-size of theclassifier allows the instruments firmware to calculate a conversionfunction. This allows pulse height size data to be converted internallyto aerodynamic size. In some known devices, some OPC manufactures havedocumented procedures that will allow this factor to be determinedexternally and the applied to convert the data after it has been taken,which is an inferior process.

Additionally, embodiments described above may include an integratedtouch-screen as a user interface. The touch-screen allows users toeasily interact with the system, giving it functionality approaching theease of use of a computer interface. Known photometers typicallycomprise membrane buttons. In some embodiments, output device 366 maycomprise an interactive touch-screen display.

Systems 300 to 700 described above may also allow Ethernetcommunication. Such innovation allows setting a network of instruments.Each instrument may be assigned a unique IP address. A single computermay communicate to a large number of instruments, sending commands ordownloading data. In prior art instruments, non-Ethernet protocols (e.g.RS232, RS3846, USB) have been used to communicate with instruments.These protocols tend to be more difficult to network.

Finally, it is noted that while the above discussion makes frequentreference to “light” as the propagated, scattered and collected medium,such use is not to be construed as limiting the invention to applicationin the visible portion of the electromagnetic spectrum. Rather, variousembodiments of the invention may encompass any portion of theelectromagnetic spectrum appropriate for a given application, including,but not limited to the ultraviolet, visible, and infrared portions ofthe electromagnetic spectrum, collimated or uncollimated.

The embodiments above are intended to be illustrative and not limiting.Although aspects of the present invention have been described withreference to particular embodiments, those skilled in the art willrecognize that changes can be made in form and detail without departingfrom the spirit and scope of the invention.

Any incorporation by reference of or other reference to documents aboveis limited such that no subject matter is incorporated that is contraryto the explicit disclosure herein. Any incorporation by reference ofdocuments above is further limited such that no claims included in thedocuments are incorporated by reference herein. Any incorporation byreference of documents above is yet further limited such that anydefinitions provided in the documents are not incorporated by referenceherein unless expressly included herein.

For purposes of interpreting the claims for the present invention, it isexpressly intended that the provisions of Section 112, sixth paragraphof 35 U.S.C. are not to be invoked unless the specific terms “means for”or “step for” are recited in a claim.

1. An instrument for measuring size segregated mass concentration of anaerosol, comprising: a first inlet for intake of an incoming aerosolflow stream containing incoming particles, the inlet including a firstadjustable inlet portion that enables passage of selected particles ofthe incoming particles, the selected particles having a size range; afirst chamber operably coupled to the adjustable inlet portion, thechamber for reception of an aerosol flow stream containing the selectedparticles and for reception of a first beam of electromagnetic radiationfor intersection with the selected particles within the first chamber; afirst detector in communication with the first chamber, the firstdetector for detection of electromagnetic radiation scattered as aresult of the intersection in the chamber of the selected particles withthe first beam of electromagnetic radiation, the first detector fordelivery of a first detector output signal; a second detector incommunication with the first chamber, the second detector for detectionof electromagnetic radiation scattered as a result of the intersectionin the chamber of the particles with the first beam of electromagneticradiation, the second detector for delivery of second detector outputsignal representative of a second characteristic of the scatteredelectromagnetic radiation; and a control system in communication withthe first detector, the control system for reception of the firstdetector output signal and for determination of a size-segregated massconcentration of the incoming aerosol flow stream based upon the firstdetector output signal and the size range of the selected particles. 2.The instrument of claim 1, wherein the first adjustable inlet portionincludes an adjustable cut-size inlet sample conditioner.
 3. Theinstrument of claim 2, wherein the adjustable cut-size inlet sampleconditioner is selected from the group consisting of an adjustableimpactor, an adjustable cyclone, and a fan with adjustable speed.
 4. Theinstrument of claim 1, wherein the first detector output signal isrepresentative of an intensity of the electromagnetic radiationscattered as a result of the intersection in the chamber.
 5. Theinstrument of claim 1, wherein the first detector is selected from thegroup consisting of a photodiode and a photomultiplier tube.
 6. Theinstrument of claim 1, wherein the control system includes an adjustableinlet portion controller for control of the adjustable inlet portion,including control of the size range of the selected particles.
 7. Theinstrument of claim 1, wherein the control system includes a signalconditioner for receipt of the first detector output signal and outputof a conditioned signal.
 8. The instrument of claim 7, wherein theconditioned signal is proportional to an intensity of theelectromagnetic radiation scattered.
 9. The instrument of claim 1,further comprising a processor for the determination of asize-segregated mass concentration of the incoming aerosol flow streambased upon the first detector output signal and the size range of theselected particles.
 10. The instrument of claim 1, wherein the controlsystem includes an output device for display, storage, or transfer ofdata relating to the size-segregated mass concentration.
 11. Theinstrument of claim 1, further comprising a filter at an exit of thechamber, the filter for capturing particles to be weighed to determinemass concentration.
 12. An instrument for measuring size segregated massconcentration of an aerosol, comprising: a chamber for reception of anincoming aerosol flow stream containing particles and for reception of abeam of electromagnetic radiation for intersection with the particleswithin the chamber; a first detector in communication with the chamber,the first detector for detection of electromagnetic radiation scatteredas a result of the intersection in the chamber of the particles with thebeam of electromagnetic radiation, the first detector for delivery of afirst detector output signal representative of a first characteristic ofthe scattered electromagnetic radiation; a second detector incommunication with the chamber, the second detector for detection ofelectromagnetic radiation scattered as a result of the intersection inthe chamber of the particles with the first beam of electromagneticradiation, the second detector for delivery of a second detector outputsignal representative of a second characteristic of the scatteredelectromagnetic radiation; and a control system in communication withthe first and second detectors, the control system for reception of thefirst and second detector output signals and for determination of asize-segregated mass concentration of the incoming aerosol flow streambased upon the first and the second detector output signals.
 13. Theinstrument of claim 12, wherein the first characteristic is an intensityof scattered electromagnetic radiation.
 14. The instrument of claim 12,wherein the first characteristic is a pulse height.
 15. The instrumentof claim 12, wherein the second characteristic is a pulse height. 16.The instrument of claim 12, wherein the second characteristic is a pulsewidth.
 17. The instrument of claim 12, wherein the control systemfurther includes a first signal conditioner adapted to condition thefirst detector output signal and a second signal conditioner adapted tocondition the second detector output signal.
 18. The instrument of claim12, wherein the control system further includes a processor fordetermination of a size-segregated mass concentration of the incomingaerosol flow stream based upon the first and the second detector outputsignals.
 19. The instrument of claim 12, wherein the control system isadapted to determine a pulse area based on a first characteristic ofpulse height and a second characteristic of pulse width, therebydetermining a particle size.
 20. The instrument of claim 12, furthercomprising a third detector adapted to detect a third characteristic.21. An instrument for measuring size segregated mass concentration of anaerosol, comprising: a first chamber for reception of a first portion ofan incoming aerosol flow stream containing first particles and forreception of a first beam of electromagnetic radiation for intersectionwith the first particles within the first chamber; a second chamber forreception of a second portion of the incoming aerosol flow streamcontaining second particles and for reception of a second beam ofelectromagnetic radiation for intersection with the second particleswithin the second chamber; a first detector in communication with thefirst chamber, the first detector for detection of electromagneticradiation scattered as a result of the intersection in the first chamberof the first particles with the first beam of electromagnetic radiation,the first detector for delivery of a first detector output signalrepresentative of a first characteristic of the scatteredelectromagnetic radiation in the first chamber; a second detector incommunication with the second chamber, the second detector for detectionof electromagnetic radiation scattered as a result of the intersectionin the second chamber of the second particles with the second beam ofelectromagnetic radiation, the second detector for delivery of a seconddetector output signal representative of a second characteristic of thescattered electromagnetic radiation in the second chamber; and a controlsystem in communication with the first and second detectors, the controlsystem for reception of the first and second detector output signals andfor determination of a size-segregated mass concentration of theincoming aerosol flow stream based upon the first and the seconddetector output signals.
 22. The instrument of claim 21, wherein thefirst characteristic is an intensity of scattered electromagneticradiation.
 23. The instrument of claim 21, wherein the secondcharacteristic is a pulse height.
 24. The instrument of claim 21,wherein the second characteristic is a pulse width.
 25. The instrumentof claim 21, wherein the control system further includes a first signalconditioner adapted to condition the first detector output signal and asecond signal conditioner adapted to condition the second detectoroutput signal.
 26. The instrument of claim 21, wherein the controlsystem further includes a processor for determination of asize-segregated mass concentration of the incoming aerosol flow streambased upon the first and the second detector output signals.
 27. Theinstrument of claim 21, wherein the control system is adapted todetermine a pulse area based on a first characteristic of pulse heightand a second characteristic of pulse width, thereby determining aparticle size.
 28. An instrument for measuring size segregated massconcentration of an aerosol, comprising: a first inlet for intake of afirst portion of an incoming aerosol flow stream containing incomingparticles, the first inlet including a first adjustable inlet portionthat enables passage of first selected particles of the incomingparticles, the first selected particles having a first size range; asecond inlet for intake of a second portion of the incoming aerosol flowstream containing incoming particles, the second inlet including asecond adjustable inlet portion that enables passage of second selectedparticles of the incoming particles, the selected particles having asecond size range; a first chamber operably coupled to the firstadjustable inlet portion, the chamber for reception of an aerosol flowstream containing the first selected particles and for reception of afirst beam of electromagnetic radiation for intersection with the firstselected particles within the first chamber; a second chamber operablycoupled to the second adjustable inlet portion, the second chamber forreception of an aerosol flow stream containing the second selectedparticles and for reception of a second beam of electromagneticradiation for intersection with the second selected particles within thesecond chamber; a first detector in communication with the firstchamber, the first detector for detection of electromagnetic radiationscattered as a result of the intersection in the first chamber of thefirst selected particles with the first beam of electromagneticradiation, the first detector for delivery of a first detector outputsignal; a second detector in communication with the second chamber, thesecond detector for detection of electromagnetic radiation scattered asa result of the intersection in the chamber of the second selectedparticles with the second beam of electromagnetic radiation, the seconddetector for delivery of a second detector output signal; and a controlsystem in communication with the first and second detectors, the controlsystem for reception of the first and second detector output signals andfor determination of a size-segregated mass concentration of theincoming aerosol flow stream based upon the first and the seconddetector output signals.
 29. The instrument of claim 28, wherein thefirst detector output represents an intensity of scatteredelectromagnetic radiation in the first chamber due to the intersectionof the first beam with the first selected particles having a first sizerange.
 30. The instrument of claim 28, wherein the second detectoroutput represents an intensity of scattered electromagnetic radiation inthe second chamber due to the intersection of the second beam with thesecond selected particles having a second size range.
 31. The instrumentof claim 28, wherein the control system further includes a first signalconditioner adapted to condition the first detector output signal and asecond signal conditioner adapted to condition the second detectoroutput signal.
 32. The instrument of claim 28, wherein the controlsystem further includes a processor for determination of asize-segregated mass concentration of the incoming aerosol flow streambased upon the first and the second detector output signals.
 33. Aninstrument for measuring size segregated mass concentration of anaerosol, comprising: a chamber for reception of an incoming aerosol flowstream containing particles and for reception of a first beam ofelectromagnetic radiation having a first wavelength and a second beam ofelectromagnetic radiation having a second fluorescence-inducingwavelength, the first and second beams for intersection with theparticles within the first chamber; a first detector in communicationwith the chamber, the first detector for detection of electromagneticradiation of the first wavelength scattered as a result of theintersection in the first chamber of the particles with the first beamof electromagnetic radiation, the first detector for delivery of a firstdetector output signal representative of a first characteristic of thescattered electromagnetic radiation; a second detector in communicationwith the chamber, the second detector operable at a bandwidth fordetection of fluoresced electromagnetic radiation emitted by theparticles after intersection with the second beam of electromagneticradiation, the second detector for delivery of a second detector outputsignal representative of the fluoresced electromagnetic radiation; and acontrol system in communication with the first and second detectors, thecontrol system for reception of the first and second detector outputsignals and for determination of a size-segregated mass concentration ofthe incoming aerosol flow stream based upon the first and the seconddetector output signals.
 34. The instrument of claim 33, wherein thesecond detector includes optical filters in front of the second detectorfor detection of fluoresced electromagnetic radiation emitted by theparticles after intersection with the second beam.